Characteristics of Deep Coal Reservoir and Key Control Factors of Coalbed Methane Accumulation in Linxing Area

Chuanqi Tao (), Yong Li, Yanbin Wang, Xiaoming Ni, Xiang Wu and Shihu Zhao
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Chuanqi Tao: School of Civil Engineering, Liaoning Petrochemical University, Fushun 113001, China
Yong Li: College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083, China
Yanbin Wang: College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083, China
Xiaoming Ni: School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China
Xiang Wu: China United Coalbed Methane Co., Ltd., Beijing 100016, China
Shihu Zhao: College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083, China

Energies, 2023, vol. 16, issue 16, 1-18

Abstract: Deep coalbed methane (CBM, commonly accepted as >1500 m) has enormous exploration and development potential, whereas the commercial development of deep CBM exploration areas wordwide has been quite limited. The Linxing area, with coals buried approximately 2000 m deep, shows great development potential. Based on a basic geological analysis of structural and hydrodynamic conditions, combining field tests of reservoir temperature and pressure and indoor measurements of maceral composition, proximate analysis, thermal maturity, porosity and permeability, the factors controlling deep CBM accumulations were discussed. The results show that the present burial depth of the No. 8 + 9 coal seam, mainly between 1698 and 2158 m, exhibits a high reservoir temperature (45.0–64.0 °C) and pressure (15.6–18.8 MPa), except for the uplift area caused by the Zijinshan magma event (with coal depth approximately 1000 m). The maximum vitrinite reflectance ( R o,max ) of the coal varies from 1.06% to 1.47%, while the magma-influenced areas reach 3.58% with a relatively high ash content of 31.3% (air-dry basis). The gas content calculated by field desorption tests shows a wide range from 7.18 to 21.64 m 3 /t. The key factors controlling methane accumulation are concluded from regional geological condition variations. The north area is mainly controlled by structural conditions and the high gas content area located in the syncline zones. The center area is dominated by the Zijinshan magma, with relatively high thermal maturity and a high gas content of as much as 14.5 m 3 /t. The south area is developed with gentle structural variations, and the gas content is mainly influenced by the regional faults. Furthermore, the groundwater activity in the eastern section is stronger than that in the west, and the hydrodynamic stagnant areas in the western are more beneficial for gas accumulation. The coals vary from 3.35% to 6.50% in porosity and 0.08 to 5.70 mD in permeability; thus, hydrofracturing considering high temperature and pressure should be applied carefully in future reservoir engineering, and the co-production of gas from adjacent tight sandstones also should be evaluated.

Keywords: deep coalbed methane; gas content; CBM accumulations; Linxing area; maceral composition (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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